KR20210073552A - Method for producing transparent polyimide film - Google Patents

Abstract

By exposing a polyimide film to the liquid for a 1st process, the residual amount of the organic solvent used for film forming of a polyimide film can be reduced. The liquid for a 1st process does not melt|dissolve a polyimide film, content of water is 80 weight% or less, It is preferable that it is a non-flammable substance. As the liquid for treatment, a liquid having a flash point of 50°C or higher, or a liquid having no flash point, or a water mixture having an alcohol content of 20% by weight or more and less than 60% by weight is used. Examples of the liquid treatment liquid having a flash point of 50° C. or higher or not exhibiting a flash point include organic fluorine-based solvents such as hydrofluoroether, glycol ether-based solvents, and the like.

Description

Method for producing transparent polyimide film

The present invention relates to a method for producing a transparent polyimide film.

With the rapid progress of electronic devices, such as a display, a solar cell, and a touch panel, thickness reduction of a device, weight reduction, and furthermore, flexibility is calculated|required. In response to these demands, the replacement of a glass material used for a substrate, a cover window, etc. with a plastic film material is being considered. In particular, in applications requiring high heat resistance, dimensional stability at high temperatures, and high mechanical strength, application of a polyimide film as a glass replacement material is being studied.

A general wholly aromatic polyimide has strong intramolecular and intermolecular charge transfer interactions, and the absorption edge wavelength reaches the visible region, so it is colored yellow or brown. In addition, the wholly aromatic polyimide is poor in solubility in organic solvents due to a rigid molecular structure, π-π stacking between molecules, and the like. Therefore, the polyimide film is generally prepared by applying a polyamic acid solution, which is a polyimide precursor, as a film on a support, removing the solvent by heating, and dehydrating and cyclizing the polyamic acid to imidize ( thermal imidization). Thermal imidization is generally performed at a high temperature of 300°C or higher.

As methods for imparting visible light transmittance and solvent solubility to polyimide, introduction of an alicyclic structure, introduction of a bent structure, introduction of a fluorine substituent, and the like are known. A soluble polyimide can also manufacture a film by the method of apply|coating a polyimide resin solution on a support body, and removing a solvent (for example, refer patent documents 1 - 3). Since the method using a polyimide resin solution does not require heating at high temperature for imidation, it is hard to generate|occur|produce coloring by heating, and there exists an advantage that a transparent polyimide film with high transparency is easy to be obtained.

Japanese Patent Laid-Open No. 2012-144603 Japanese Patent Laid-Open No. 2016-132686 WO2017/175869 International publication pamphlet

When a transparent polyimide film is produced using a solution of a solvent-soluble polyimide resin disclosed in Patent Documents 1 to 3, etc., the solvent is hardly volatilized from the film, and when a long time high temperature treatment is performed to reduce the amount of residual solvent, the polyimide film It causes a decrease in quality or production efficiency due to the coloring of Therefore, it is desired to reduce the residual solvent of a transparent polyimide film simply, without impairing transparency.

In the manufacturing method of the transparent polyimide film of this invention, the polyimide film containing a residual organic solvent is exposed to the liquid for a 1st process. The polyimide film containing an organic solvent is obtained by apply|coating the solution which the polyimide resin melt|dissolved in the organic solvent on a support body, for example, and removing a part of organic solvent. After peeling a polyimide membrane from a support body, you may expose a polyimide membrane to the liquid for a 1st process.

As an organic solvent used for film forming of a polyimide film, it is preferable that a flash point is 50 degreeC or more, or the thing which does not show a flash point is preferable. As for the boiling point of the organic solvent used for film forming of a polyimide film|membrane, 80 degrees C or less is preferable. Dichloromethane may be sufficient as the organic solvent used for film-forming of a polyimide film.

The 1st liquid for a process used for reduction of the residual organic solvent in a polyimide film|membrane does not melt|dissolve a polyimide film, It is an organic solvent, or a water content of 80 weight% or less, and a mixed liquid of an organic solvent. The liquid for the first treatment is preferably a non-flammable material, and a liquid having a flash point of 50° C. or higher or no flash point, or a water/alcohol mixture having an alcohol content of 20% by weight or more and less than 60% by weight is preferably used. The liquid for a 1st process may contain organic fluorine solvents, such as hydrofluoroether, and may contain glycol ether solvents, such as glycol ethers, dialkyl glycol ethers, and glycol ether acetates.

As a method of exposing a polyimide film to the liquid for a process, the method of making a liquid for a process and a polyimide film directly contact by immersion etc. is mentioned. You may expose a polyimide film to the liquid for a process by exposing a polyimide film to the gas atmosphere of the liquid for a process.

After the treatment with the first processing liquid, the processing liquid may be removed from the polyimide film by heating. Moreover, you may expose a polyimide film to the liquid for a 2nd process of a composition different from the liquid for a 1st process.

In the method of this invention, the amount of residual solvent can be reduced by exposing the polyimide film containing a residual solvent to a predetermined processing solution. By speeding up the solvent removal of the transparent polyimide film, productivity is improved, and facilities such as a high-temperature heating furnace are also unnecessary, so that cost reduction can be expected.

[Polyimide]

A polyimide is generally obtained by obtaining polyamic acid by superposition|polymerization of tetracarboxylic dianhydride (it may describe as "acid dianhydride" hereafter) and diamine, and dehydrating cyclization of polyamic acid. That is, the polyimide has a structure derived from tetracarboxylic dianhydride and a structure derived from diamine.

<Composition of polyamic acid and polyimide>

Examples of the acid dianhydride usable as a raw material for polyamic acid and polyimide include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1 ,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,1'-bicyclohexane-3,3',4,4 'Tetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,2' ,3,3'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4- Dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1 ,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3 ,3,3-hexafluoropropane dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride Water, 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, 2,2-bis{4-[3-(1,2-dicarboxy)phenoxy Cy]phenyl}propane dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy] Phenyl}ketone dianhydride, 4,4'-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, 4,4'-bis[3-(1,2-dicarboxy)phenoxy ]biphenyl dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy Cy]phenyl}ketone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy] Phenyl}sulfone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl }sulfide dianhydride, 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-hexaflupropane dianhydride, 2 ,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-propane dianhydride, 2,3,6,7-naphthalenetetra Carboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxyl Acid dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxyl Acid dianhydride, bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid)-1,4-phenylene ester, bis(1,3-dihydro-1,3 -dioxo-5-isobenzofurancarboxylic acid)-(2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl)ester can be heard

Examples of diamines usable as a raw material for polyamic acid and polyimide include 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4 '-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 4 ,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenylsulfone; 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl Methane, 3,4'-diaminodiphenylmethane, 2,2-di(3-aminophenyl)propane, 2,2-di(4-aminophenyl)propane, 2-(3-aminophenyl)-2- (4-aminophenyl) propane, 1,4-diamino-2-fluorobenzene, 1,4-diamino-2,3-difluorobenzene, 1,4-diamino-2,5-difluoro Robenzene, 1,4-diamino-2,6-difluorobenzene, 1,4-diamino-2,3,5-trifluorobenzene, 1,4-diamino-2,3,5, 6-tetrafluorobenzene, 1,4-diamino-2-(trifluoromethyl)benzene, 1,4-diamino-2,3-bis(trifluoromethyl)benzene, 1,4-diamino -2,5-bis(trifluoromethyl)benzene, 1,4-diamino-2,6-bis(trifluoromethyl)benzene, 1,4-diamino-2,3,5-tris(tri Fluoromethyl)benzene, 1,4-diamino-2,3,5,6-tetrakis(trifluoromethyl)benzene, 2-fluorobenzidine, 3-fluorobenzidine, 2,3-difluoro Benzidine, 2,5-difluorobenzidine, 2,6-difluorobenzidine, 2,3,5-trifluorobenzidine, 2,3,6-trifluorobenzidine, 2,3,5,6- Tetrafluorobenzidine, 2,2'-difluorobenzidine, 3,3'-difluorobenzidine, 2,3'-difluorobenzidine, 2,2',3-trifluorobenzidine, 2,3 ,3'-trifluorobenzidine, 2,2',5-trifluorobenzyl Dean, 2,2',6-trifluorobenzidine, 2,3',5-trifluorobenzidine, 2,3',6,-trifluorobenzidine, 2,2',3,3'-tetra Fluorobenzidine, 2,2',5,5'-tetrafluorobenzidine, 2,2',6,6'-tetrafluorobenzidine, 2,2',3,3',6,6'-hexa Fluorobenzidine, 2,2',3,3',5,5',6,6'-octafluorobenzidine, 2-(trifluoromethyl)benzidine, 3-(trifluoromethyl)benzidine, 2 ,3-bis(trifluoromethyl)benzidine, 2,5-bis(trifluoromethyl)benzidine, 2,6-bis(trifluoromethyl)benzidine, 2,3,5-tris(trifluoromethyl) ) benzidine, 2,3,6-tris (trifluoromethyl) benzidine, 2,3,5,6-tetrakis (trifluoromethyl) benzidine, 2,2'-bis (trifluoromethyl) benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,3'-bis(trifluoromethyl)benzidine, 2,2',3-bis(trifluoromethyl)benzidine, 2,3,3' -tris(trifluoromethyl)benzidine, 2,2',5-tris(trifluoromethyl)benzidine, 2,2',6-tris(trifluoromethyl)benzidine, 2,3',5-tris (trifluoromethyl)benzidine, 2,3',6,-tris(trifluoromethyl)benzidine, 2,2',3,3'-tetrakis(trifluoromethyl)benzidine, 2,2', 5,5'-tetrakis(trifluoromethyl)benzidine, 2,2',6,6'-tetrakis(trifluoromethyl)benzidine2,2-di(3-aminophenyl)-1,1, 1,3,3,3-hexafluoropropane, 2,2-di(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2-(3-aminophenyl) -2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 1,1-di(3-aminophenyl)-1-phenylethane, 1,1-di( 4-aminophenyl)-1-phenylethane, 1-(3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane, 1,3-bis(3-aminophenoxy)benzene, 1, 3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl ) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1 ,4-bis(4-aminobenzoyl)benzene, 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(3-amino-α, α-ditrifluoromethylbenzyl)benzene, 1,3-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, 1,4-bis(3-amino-α,α-ditri Fluoromethylbenzyl)benzene, 1,4-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, 2,6-bis(3-aminophenoxy)benzonitrile, 2,6-bis (3-aminophenoxy)pyridine, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)biphenyl Cy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl] Sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[ 4-(4-aminophenoxy)phenyl]ether, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane , 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) )phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4) -Aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3 -bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4 -bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4 '-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4' -bis[4-(4-a) mino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenylsulfone, 3,3'-diamino-4,4 '-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino- 4-biphenoxybenzophenone, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobindane, 6,6'-bis (4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobindane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3- Bis(4-aminobutyl)tetramethyldisiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α,ω-bis(3-aminobutyl)polydimethylsiloxane, bis(aminomethyl)ether, bis (2-aminoethyl)ether, bis(3-aminopropyl)ether, bis(2-aminomethoxy)ethyl]ether, bis[2-(2-aminoethoxy)ethyl]ether, bis[2-(3) -Aminoprotoxy)ethyl]ether, 1,2-bis(aminomethoxy)ethane, 1,2-bis(2-aminoethoxy)ethane, 1,2-bis[2-(aminomethoxy)ethoxy ]ethane, 1,2-bis[2-(2-aminoethoxy)ethoxy]ethane, ethylene glycol bis(3-aminopropyl) ether, diethylene glycol bis(3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane , 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diamino Cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di(2-aminoethyl)cyclohexane, 1,3-di(2-aminoethyl)cyclohexane, 1 ,4-di(2-aminoethyl)cyclohexane, bis(4-aminocyclohexyl)methane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,5-bis(aminomethyl) bicyclo[2.2.1]heptane.

In order to obtain a polyimide which has high visible light transmittance and is soluble in organic solvents, as an acid dianhydride, alicyclic tetracarboxylic acids such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) Fluorine-containing aromatic tetracarboxylic dianhydride such as dianhydride and 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA) ; and/or p-phenylenebis(trimellitic anhydride) (TMHQ), bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3 ,3',5,5'-hexamethylbiphenyl-4,4'diyl (alias 2,2',3,3',5,5'-hexamethyl-biphenylenebis(trimellitic dianhydride) It is preferable to use an aromatic tetracarboxylic dianhydride in which two carbonyl groups are bonded to other aromatic rings such as (TAHMBP), and as the diamine, 2,2'-bis(trifluoromethyl)benzidine (TFMB) Aromatics in which an amino group is bonded to each other aromatic ring such as fluorine-containing aromatic diamines (especially fluoroalkyl-substituted benzidine) and/or 3,3'-diaminodiphenylsulfone (3,3'-DDS) Preference is given to using diamines.

From the viewpoint of ensuring transparency, solvent solubility and mechanical strength of the polyimide film, as the acid dianhydride component of the polyimide, CBDA, 6FDA, BPDA, TMHQ, TAHMBP, etc. are preferable, and as the diamine component, TFMB, 3,3' -DDS etc. are preferable. In total 100 mol% of the acid dianhydride component of a polyimide, 20 mol% or more is preferable, as for content of 6FDA, 30 mol% or more is more preferable, 35 mol% or more, 40 mol% or more, 45 mol% or more Or 50 mol% or more may be sufficient. 100 mol% may be sufficient as content of 6FDA, and 90 mol% or less, 80 mol% or less, or 70 mol% or less may be sufficient as it. In total 100 mol% of the diamine component of a polyimide, 20 mol% or more is preferable, as for content of TFMB, 30 mol% or more is more preferable, 40 mol% or more is still more preferable, 50 mol% or more, 60 mol % or more or 70 mol% or more may be sufficient. 100 mol% may be sufficient as content of TFMB, and 95 mol% or less, 90 mol% or less, 85 mol% or less, or 80 mol% or less may be sufficient as it.

In particular, in order to obtain a polyimide resin having high solubility in organic solvents, it is preferable to use TFMB or a combination of TFMB and 3,3'-DDS as the diamine. In this case, as the acid dianhydride, a combination of 6FDA and CBDA, a combination of 6FDA and BPDA, a combination of 6FDA and TMHQ, a combination of 6FDA and TMHQ and BPDA, a combination of 6FDA and TAHMBP, and the like are preferable.

[Production of polyimide film]

<Preparation of polyamic acid solution>

A polyimide is obtained by dehydration cyclization of the polyamic acid which is a polyimide precursor. All known methods can be used for the manufacturing method of a polyamic acid, and it is not specifically limited. For example, an acid dianhydride and a diamine are dissolved in an organic solvent in approximately equimolar amounts (a molar ratio of 95:100 to 105:100), and stirred until polymerization of the acid dianhydride and diamine is completed to complete the polyamic acid solution. this is obtained The concentration of the polyamic acid solution is usually 5 to 35% by weight, preferably 10 to 30% by weight. In the case of a concentration in this range, a polyamic acid solution having an appropriate molecular weight and viscosity is obtained. When adding multiple types of diamines or multiple types of acid dianhydrides, you may add at once, and may divide and add the frequency|count of addition into multiple times.

The organic solvent used for polymerization of polyamic acid does not react with diamine and an acid dianhydride, but if it is a solvent which can melt|dissolve polyamic acid, it will not specifically limit. Examples of the organic solvent include a urea-based solvent such as methylurea and N,N-dimethylethylurea, a sulfoxide or sulfone-based solvent such as dimethylsulfoxide, diphenylsulfone, and tetramethylsulfone, and N,N-dimethylacetamide (DMAc) Amides such as , N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, and hexamethylphosphoric acid triamide Solvents, halogenated alkyl solvents such as chloroform and dichloromethane, aromatic hydrocarbon solvents such as benzene and toluene, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, p- Ether solvents, such as cresol methyl ether, are mentioned. Usually, these solvents are used individually or in combination of 2 or more types as needed. From the viewpoints of solubility of polyamic acid and polymerization reactivity, DMAc, DMF, NMP and the like are preferably used.

<Preparation of polyimide resin>

As a method for producing a polyimide film from a polyamic acid solution, (i) a method in which a polyamic acid solution is applied as a film on a support, the solvent is removed by drying, and the polyamic acid is imidized; and (ii) imidization in the state of a polyamic acid solution to prepare a polyimide resin, apply the polyimide resin solution as a film on a support, and dry and remove the solvent. Any method of said (i) (ii) is applicable to the polyimide soluble in an organic solvent. The method of said (ii) is preferable because it does not require heating at high temperature for imidation, and transparency high polyimide film is obtained.

As a method of preparing a polyimide solution from a polyamic-acid solution, a dehydrating agent, an imidation catalyst, etc. are added to a polyamic-acid solution, and the method of advancing imidation in solution (chemical imidation) is mentioned. In order to accelerate advancing of imidation, you may heat the polyamic-acid solution.

Although the polyimide solution obtained by imidation of a polyamic acid can also be used as film forming dope as it is, it is preferable to make polyimide resin precipitate as a solid thing once. By mixing a polyimide solution and a poor solvent, polyimide resin is precipitated. A poor solvent is a poor solvent of polyimide resin, It is preferable to mix with the solvent which is melt|dissolving polyimide resin, water, alcohol, etc. are mentioned. Since a small amount of an imidation catalyst, a dehydrating agent, etc. may remain|survive in the polyimide resin which precipitated, it is preferable to wash|clean with a poor solvent. It is preferable that the polyimide resin after precipitation and washing|cleaning removes a poor solvent by vacuum drying, hot air drying, etc.

By precipitating the polyimide resin as a solid, impurities and residual monomer components, dehydrating agents, imidization catalysts, and the like generated during polymerization of polyamic acid can be washed and removed. Therefore, a polyimide film excellent in transparency and mechanical properties is obtained. In addition, a solvent suitable for film forming conditions can be applied by once precipitating polyimide resin as a solid material.

<Polyimide solution>

By dissolving polyimide resin in an organic solvent, a polyimide solution (it is also mentioned film forming dope) is prepared. The organic solvent is not particularly limited as long as it is soluble in the polyimide resin. For example, a urea-based solvent, a sulfoxide or sulfone-based solvent, an amide-based solvent, and a halogenated organic solvent used for polymerization of polyamic acid. and alkyl solvents, aromatic hydrocarbon solvents, and ether solvents. In addition to these, ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone and methyl cyclohexanone are also used for polyimide resin It is suitably used as a solvent.

From a viewpoint of removing a solvent from a polyimide solution and simplifying the facilities at the time of producing a polyimide film, it is preferable that the flash point of the organic solvent which melt|dissolves a polyimide resin is 50 degreeC or more, or does not show a flash point. When an organic solvent shows a flash point, it is preferable that the flash point of an organic solvent is higher than the heating temperature in the manufacturing process of a polyimide film. When the drying temperature by heating is considered, 70 degreeC or more is preferable and, as for the flash point of an organic solvent, 100 degreeC or more is more preferable. It is so preferable that the flash point of an organic solvent is high, and 150 degreeC or more, 200 degreeC or more, or 150 degreeC or more may be sufficient. It is particularly preferred that the organic solvent does not exhibit a flash point. From a viewpoint of facilitating solvent removal at low temperature, 80 degrees C or less is preferable, as for the boiling point of the organic solvent which melt|dissolves polyimide resin, 60 degrees C or less is more preferable, and 50 degrees C or less is still more preferable. Since it does not show a flash point and has a low boiling point, dichloromethane is especially preferable as an organic solvent.

In order to provide processing characteristics and various functionalities to a polyimide film, you may mix|blend an organic or inorganic low molecular or high molecular compound with film forming dope. For example, an ultraviolet absorber, a crosslinking agent, a dye, a surfactant, a leveling agent, a plasticizer, microparticles|fine-particles, a sensitizer, etc. can be used. As for the solid content concentration of film-forming dope, 5 to 30 weight% is preferable, and, as for the viscosity in 25 degreeC to film-forming dope, 0.5 Pa*s - 60 Pa*s are preferable. 60 weight part or more is preferable, as for content of polyimide resin with respect to 100 weight part of solid content of film forming dope, 70 weight part or more is more preferable, 80 weight part or more is still more preferable.

As a support body which apply|coats film forming dope, metal substrates, such as a glass substrate and SUS, a metal drum, a metal belt, a plastic film, etc. can be used. From a viewpoint of productivity improvement, it is preferable to manufacture a film by roll-to-roll using, as a support body, endless supports, such as a metal drum, a metal belt, or a long plastic film. When using a plastic film as a support body, what is necessary is just to select suitably the material which does not melt|dissolve in the solvent of film forming dope, As a plastic material, polyethylene terephthalate, polycarbonate, a polyacrylate, a polyethylene naphthalate, etc. are used. As a coating method, bar coating, die coating, spin coating, etc. can be applied without specific limitation.

What is necessary is just to set the application|coating thickness on a support body according to the thickness of the polyimide film made into the objective. The thickness of a polyimide film is 5 micrometers or more, for example. The thickness of the polyimide film is preferably from 20 µm to 100 µm, more preferably from 30 µm to 90 µm, and from 40 µm to 80 µm from the viewpoint of providing a film with both self-support and flexibility and high transparency. It is more preferable, and 50 micrometers - 80 micrometers are especially preferable. As for the thickness of the transparent polyimide film as a cover film use of a display, 50 micrometers or more are preferable.

A polyimide membrane is obtained by apply|coating a polyimide solution on a support body, and drying off a solvent. When drying a solvent, it is preferable to heat. As for heating temperature, a solvent should just be removable, and it is 30 degreeC or more or 50 degreeC or more, for example. Although the upper limit of heating temperature is not specifically limited, In order to suppress coloring by heating and to obtain a polyimide film with high transparency, 250 degrees C or less is preferable, and 220 degrees C or less is more preferable. In order to improve the removal efficiency of a solvent, after drying to some extent or more, you may peel and dry a polyimide membrane from a support body. In order to accelerate removal of a solvent, you may heat under reduced pressure.

Although the above demonstrated centering around the example of forming a polyimide film using a polyimide resin solution, a polyamic acid solution may be apply|coated as a film|membrane on a support body, imidation may be performed by heating, and a polyimide film may be formed. Also in this case, after heating on a support body and removing an organic solvent to some extent, you may peel a film|membrane from a support body and heat.

[Residual solvent reduction treatment]

(i) a method in which a polyamic acid solution is applied as a film on a support and the solvent is removed by drying and imidization of the polyamic acid; and (ii) coating the polyimide resin solution as a film on the support and drying the solvent off, it is difficult to completely remove the organic solvent from the polyimide film, and a certain amount of the organic solvent is present in the film. it remains In particular, in the method (ii), since high-temperature heating for imidization is not performed, the organic solvent tends to remain in the polyimide film. In a polyimide film having a large thickness (for example, 30 µm or more), when the organic solvent near the surface layer volatilizes, volatilization of the solvent near the center in the thickness direction can be prevented. In some cases, it is difficult to make it small enough.

By exposing the polyimide film in which the organic solvent used for film forming (organic solvent of film forming dope) remains to a liquid for treatment, removal of the organic solvent in the film is accelerated, and the amount of residual solvent can be reduced at a low temperature and in a short time. .

<Liquid for 1st process>

The processing liquid (1st processing liquid) used for the removal of the organic solvent used for film forming does not melt|dissolve a polyimide film, and is an organic solvent or the organic solvent containing 80 weight% or less of water, and a mixture of water. 70 weight% or less is preferable and, as for content of the water in the liquid for a process, 60 weight% or less is more preferable.

It is preferable that the liquid for treatment is a non-flammable material. Specifically, an alcohol/water mixture having an alcohol content of 20% by weight or more and less than 60% by weight, an organic halogen solvent, a glycol ether solvent, or the like, a liquid having a flash point of 50°C or higher or a liquid having no flash point is used. The flash point of the liquid for treatment may be 70°C or higher, 100°C or higher, 150°C or higher, 200°C or higher, or 250°C or higher. By using a non-flammable substance as a liquid for a process, the facility for a residual solvent reduction process can be simplified.

(Liquid for alcohol-based treatment)

As the alcohol in the alcohol/water mixture, a lower alcohol having 1 to 6 carbon atoms is preferable, and among these, alcohols having 1 to 3 carbon atoms such as methanol, ethanol and isopropyl alcohol are preferable. Since the molecular size of a lower alcohol is small, it can be easily replaced with the molecule|numerator of the residual solvent in a polyimide film|membrane, and a boiling point is low and it can be easily removed.

The liquid for processing may contain 2 or more types of alcohol. The combination of 2 or more types of alcohols may be a combination of C2 or less alcohol and C3 or more alcohol. Methanol and ethanol are mentioned as C2 or less alcohol. Examples of the alcohol having 3 or more carbon atoms include n-propanol, isopropyl alcohol, and n-butanol. Among these, the combination of C2 or less alcohol and isopropyl alcohol is preferable. As C2 or less alcohol, you may contain both methanol and ethanol. In the combination of an alcohol having 2 or less carbon atoms and an alcohol having 3 or less carbon atoms, the amount (concentration) of the alcohol having 2 or less carbon atoms in the treatment liquid is preferably 1 to 99% by weight based on the total amount of the alcohol.

The liquid for processing may contain liquid components other than alcohol and water. When the liquid for treatment is an alcohol/water mixed liquid, the total concentration of alcohol and water is preferably 60% by weight or more, and preferably 70% by weight or more.

(Liquid for organic halogen-based treatment)

Examples of the organic halogen solvent used as the processing liquid include organic fluorine-based solvents, organic chlorine-based solvents and organic bromine-based solvents. The organic halogen solvent may contain a plurality of halogen species. The organic halogen solvent is a liquid at room temperature, and one that does not dissolve the polyimide film can be used without any particular limitation. 100 degrees C or less is preferable and, as for the boiling point of the organic halogen solvent used as a liquid for a process, 80 degrees C or less is more preferable.

From the standpoint of excellent removability of residual solvent, the organic fluorine-based solvent used as the liquid for treatment is preferably an organic fluorine-based solvent such as perfluorocarbon, hydrofluorocarbon, perfluoroether or hydrofluoroether. Especially, since there is little environmental load, hydrofluoroether is preferable.

Examples of the hydrofluoroether include 2,2,2-trifluoroethylmethyl ether, 2,2,2-trifluoroethyldifluoromethyl ether, 2,2,3,3,3-pentafluoropropylmethyl Ether, 2,2,3,3,3-pentafluoropropyldifluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether , 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2- Trifluoroethyl ether, difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl methyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, 2 ,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetra Fluoropropyl ether, hexafluoroisopropyl methyl ether, 1,1,3,3,3-pentafluoro-2-trifluoromethylpropyl methyl ether, 1,1,2,3,3,3-hexa Fluoropropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 2,2,3,4,4,4-hexafluorobutyldifluoromethyl ether, 1,1 ,2,2,3,3,3-heptafluoropropyl methyl ether, (1,1,2,2,3,3,4,4-octafluoropentyl) allyl ether, (1,1,2, 2-tetrafluoroethyl) allyl ether, heptafluoro-2-propyl allyl ether, bis (trifluoroethoxy) ethane, ethoxytrifluoroethoxyethane, methoxytrifluoroethoxyethane, 1, 1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane, 1,1,1,2,2,3,4, 5,5,5-Decafluoro-3-ethoxy-4-trifluoromethyl-pentane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3- Propoxy-4-trifluoromethyl-pentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2-difluoroethyl-1, 1,2,2-tetrafluoropropyl ether, 2,2-difluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,2'H,3H-decafluorodipropyl ether , 1,1,1,2,3,3-hexafluoro Ropropyl-2,2-difluoroethyl ether, isopropyl 1,1,2,2-tetrafluoroethyl ether, propyl 1,1,2,2-tetrafluoroethyl ether, 1H,1H,5H- Perfluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1H,1H,2'H-perfluorodipropyl ether, 1H-perfluorobutyl-1H-perfluoroethyl ether, methyl purple Luoropentyl ether, methyl perfluorohexyl ether, methyl 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)propyl ether, 1,1,2,3,3,3- Hexafluoropropyl 2,2,2-trifluoroethyl ether, ethyl 1,1,2,3,3,3-hexafluoropropyl ether, 1H,1H,5H-octafluoropentyl 1,1,2 ,2-tetrafluoroethyl ether, 1H,1H,2'H-perfluorodipropyl ether, heptafluoropropyl1,2,2,2-tetrafluoroethyl ether, 1,1,2,2-tetra Fluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, ethyl nonafluoro and robutyl ether, ethyl nonafluoro isobutyl ether, methyl nonafluoro butyl ether, and methyl nonafluoro isobutyl ether. Among these, 1,1,2,2,3,3,3-heptafluoropropylmethyl ether, 1,1-difluoroethyl-2,2,2-trifluoroethyl ether, methylnonafluorobutyl Hydrofluoroethers that do not exhibit a flash point such as ether and ethylnonafluorobutyl ether are preferred. Among these, methyl nonafluorobutyl ether and ethyl nonafluorobutyl ether are preferable because of a small global warming coefficient and little environmental load.

The liquid for organic halogen-based treatment may contain an organic chlorine-based solvent in addition to the organic fluorine-based solvent. Examples of the organic chlorine-based solvent include chlorinated hydrocarbons. Since it is a low boiling point and the residual solvent removal effect of a polyimide film|membrane is high, C1-C6 chlorinated hydrocarbon is preferable. 4 or less are preferable and, as for carbon number of a chlorinated hydrocarbon, 2 or less are more preferable.

Specific examples of chlorinated hydrocarbons include chlorinated methanes (dichloromethane, chloroform and carbon tetrachloride), chlorinated ethanes (1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1, 2-trichloroethane, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, etc., pentachloroethane and hexachloroethane), chlorinated ethylene (1,1-dichloroethylene) , cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, 1,1,2-trichloroethylene and tetrachloroethylene), chlorinated propanes (1,2-dichloropropane, 1,2,3) -trichloropropane etc.) and chlorinated propenes (1,2-dichloropropene, cis-1,3-dichloropropene, trans-1,3-dichloropropene, etc.) are mentioned. Especially, since the solubility of a polyimide is low and the residual solvent removal effect is high, chlorinated ethylene is preferable, and trans-1,2-dichloroethylene is especially preferable.

When the liquid for treatment contains an organic fluorine-based solvent and an organic chlorine-based solvent, it is preferably an azeotropic composition. The liquid for processing may contain solvents other than organic fluorine solvents, such as alcohol. It is preferable that the liquid for a process contains 60 weight% or more of organic halogen solvents. 70 weight% or more, 80 weight% or more, 90 weight% or more, or 95 weight% or more may be sufficient as content of the organic halogen solvent in the liquid for a process.

As mentioned above, it is preferable that the flash point of the liquid for a process does not show 50 degreeC or more or a flash point. Even when one or more types of organic halogen solvents have flammability, by mixing with one or more types of non-flammable solvents, a flash point can be made into 50 degreeC or more or non-flammability. For example, even when chlorinated hydrocarbons have flammability, the liquid for treatment can be made non-flammable by mixing with a non-flammable fluorine-based solvent. Examples of the mixed halogenated organic solvent having a flash point of 50° C. or higher or no flash point and having an azeotropic composition include those having chlorinated hydrocarbons and hydrofluoroethers in a ratio of 5 to 70:95 to 30.

(Liquid for glycol ether treatment)

Examples of the glycol ether solvent used as the processing liquid include glycol ethers, dialkyl glycol ethers, and glycol ether esters.

Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethylhexyl ether, ethylene glycol monophenyl ether. , ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monoethylhexyl ether , Diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, propylene glycol monohexyl ether, propylene glycol monoethyl Hexyl ether, propylene glycol monophenyl ether, propylene glycol monobenzyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monohexyl ether , Dipropylene glycol monoethylhexyl ether, dipropylene glycol monophenyl ether, dipropylene glycol monobenzyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and the like.

Specific examples of the dialkyl glycol ethers include ethylene glycol dimethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol. Dipropyl ether, diethylene glycol methyl propyl ether, diethylene glycol ethyl propyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl butyl ether, diethylene glycol ethyl butyl ether, diethylene glycol propyl butyl ether, diethylene glycol diphene Tyl ether, diethylene glycol methyl pentyl ether, diethylene glycol ethyl pentyl ether, diethylene glycol propyl pentyl ether, diethylene glycol butyl pentyl ether, etc. are mentioned.

As glycol ether ester, the acetate ester (glycol ether acetates) of glycol ether is preferable. Specific examples of glycol ether acetates include ethylene glycol monoethyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monohexyl ether acetate, ethylene glycol monoethyl hexyl ether acetate, and ethylene glycol monophenyl ether. glycol ether acetates such as acetate, ethylene glycol monobenzyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol butyl ether acetate, and dipropylene glycol methyl ether acetate; have.

Among the above-mentioned, since the flash point is high (or does not show a flash point) and the removability of the residual solvent in a polyimide film is high, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether , triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, diethylene glycol monohexyl ether, and diethylene glycol dibutyl ether are preferable, and among these, the organic solvent removal property in the polyimide film Diethylene glycol monobutyl ether is especially preferable at the point which is excellent in this.

It is preferable that the liquid for a process contains 60 weight% or more of glycol ether type solvent. 70 weight% or more, 80 weight% or more, 90 weight% or more, or 95 weight% or more may be sufficient as content of the glycol ether type solvent in the liquid for a process.

The liquid for a process may contain organic solvents other than a glycol ether type solvent, or water. The glycol ether solvent has high miscibility with water, and by mixing the glycol ether solvent and water, the flash point can be increased or the flash point can be not exhibited. Further, since glycol ether and water are azeotropic, it is easy to remove the treatment liquid remaining in the polyimide film by being replaced with the residual solvent or the treatment liquid adhering to the surface of the polyimide film.

When the liquid for treatment further contains water in the glycol ether-based solvent, the content of water is preferably 2 to 40% by weight, more preferably 3 to 30% by weight. 70 weight% or more is preferable, as for the sum total of content of the glycol ether type solvent and water in the liquid for a process, 80 weight% or more is more preferable, 85 weight% or more, or 90 weight% or more may be sufficient. The liquid for a process may contain additives, such as an organic solvent other than a glycol ether type solvent and water, surfactant, and an antifoamer.

<Exposure to liquid for treatment of polyimide film>

The method of exposing the polyimide film containing the residual solvent to the liquid for treatment is not particularly limited, and the polyimide film may be immersed in the liquid for treatment, the liquid for treatment may be sprayed onto the polyimide film by spraying, or by a bar coater or the like. You may apply|coat the liquid for a process to the surface of a polyimide film|membrane. You may expose a polyimide film in the gas atmosphere in which the liquid for a process was vaporized. For example, a polyimide film may be exposed to the vapor|steam or mist of the liquid for a process, and bases, such as air or nitrogen gas, may be bubbled into the liquid for a process, and it is good also as an atmosphere containing the vapor|steam of the liquid for a process.

Exposure to the liquid for a process of a polyimide film|membrane may be performed in the state in which the polyimide film was laminated|stacked on the support body, and may be performed after peeling a polyimide film from a support body. From a viewpoint of improving the removal efficiency of a residual solvent, it is preferable to expose the polyimide film peeled from the support body to the liquid for a process.

The temperature at the time of exposing the polyimide film containing a residual solvent to the liquid for a process is 0-150 degreeC, for example, Preferably it is 15-80 degreeC, More preferably, it is 20-70 degreeC. You may process under heating. When the heating temperature is higher, the replacement of the residual solvent and the processing liquid in the film is promoted, and the removal efficiency of the residual solvent tends to be improved. The heating temperature should just be between room temperature (for example, 25 degreeC) and the boiling point of the liquid for a process to be used. The heating temperature is preferably 30°C or higher, and may be 35°C or higher, 40°C or higher, 45°C or higher, or 50°C or higher. From a viewpoint of suppressing volatilization of the liquid for a process, boiling point -10 degreeC or less is preferable.

When processing under pressure, it is below the boiling point in the said pressure, and you may heat to the temperature more than the boiling point in normal pressure in the range which does not affect a polyimide film or an optical characteristic. When immersing a polyimide membrane in the liquid for a process, you may perform ultrasonic irradiation for the purpose of the improvement of the residual solvent removal efficiency by substitution of a solvent, etc.

The exposure time may be appropriately set according to the processing temperature and the like, and is, for example, 30 seconds to 120 minutes, preferably 1 minute to 60 minutes, more preferably 3 minutes to 45 minutes, and still more preferably 5 minutes to 30 minutes. By setting it as the said range, coexistence of the sufficient removal effect of a residual solvent and productivity can be anticipated.

[After treatment]

The residual amount of the organic solvent used for film forming can be reduced by exposing a polyimide film to the liquid for a process as mentioned above. Immediately after the exposure treatment, since the treatment liquid adheres to the surface of the polyimide film, the liquid adhering to the surface may be removed by heating, air blowing, washing with water, or the like. When heating, room temperature - 200 degreeC are preferable and, as for heating temperature, 70 degreeC - 180 degreeC are more preferable. Although what is necessary is just to set a heating time suitably according to heating temperature, from a viewpoint of productivity improvement and removal of a solvent, 1 minute - 120 minutes are preferable, and 5 minutes - 90 minutes are more preferable.

In order to remove the liquid for treatment (liquid for first treatment) used in order to reduce the residual amount of the organic solvent used for film forming from the polyimide film, even if a treatment of exposing to another liquid for treatment (liquid for second treatment) is performed do.

The liquid for a 2nd process is a mixture of the organic solvent which does not melt|dissolve a polyimide film, or the organic solvent containing 80 weight% or less of water, and water similarly to the liquid for a 1st process. 70 weight% or less is preferable and, as for content of the water in the liquid for a 2nd process, 60 weight% or less is more preferable. It is preferable that the liquid for a 2nd process is a non-flammable material similarly to the liquid for a 1st process. Specifically, an alcohol/water mixture having an alcohol content of 20% by weight or more and less than 60% by weight, an organic halogen solvent, a glycol ether solvent, or the like, a liquid having a flash point of 50°C or higher or a liquid having no flash point is used. By using a non-flammable substance as a liquid for a 2nd process, the facility for a residual solvent reduction process can be simplified.

Specific examples of the second processing liquid are the same as those described above as an example of the first processing liquid. As the second processing liquid, a liquid having a composition different from that of the first processing liquid is used. As the liquid for the first treatment, a liquid having high removability of an organic solvent (an organic solvent exhibiting solubility in polyimide) used for forming the polyimide film is used, and as the liquid for the second treatment, it is less volatile than the liquid for the first treatment. It is preferable to use a higher one. For example, by performing exposure treatment with an organic halogen-based first treatment liquid containing an organic fluorine-based solvent such as hydrofluoroether, and then treating with a second treatment liquid containing alcohol and water, The liquid for the first treatment remaining in the polyimide film can be removed.

Since a large amount of the organic solvent used for film formation of the polyimide film remains inside the polyimide film in the thickness direction, it is preferable that the liquid for the first treatment has sufficient removability even for the organic solvent remaining inside the polyimide film. . On the other hand, in the polyimide film after exposure to the liquid for a 1st process, since many 1st liquid for a process exist in surface layer vicinity of a polyimide film, it can be easily replaced with the liquid for a 2nd process. Therefore, the residual amount of the liquid for a 1st process can be reduced easily by using a liquid with high volatility like an alcohol/water mixture system as a liquid for 2nd process.

The method of exposing the polyimide film to the liquid for the second treatment is not particularly limited, and similarly to the exposure to the liquid for the first treatment, immersion, spraying, coating, treatment by steam or mist, etc. are applicable. The processing time and the processing temperature are preferably in the same ranges as those described above for the exposure treatment to the first processing liquid. After the exposure treatment to the liquid for the second treatment, the liquid adhering to the surface may be removed by heating, air blowing, washing with water, or the like.

[Characteristics and uses of polyimide film]

The polyimide film obtained by the above can be applied to the various uses for which a polyimide film is generally used, such as substrate materials, such as a flexible printed wiring board and a display, and cover windows for displays. A polyimide film may be transparent in visible light, and 70 % or more or 80 % or more may be sufficient as the light transmittance in wavelength 400 nm, for example.

Example

Hereinafter, the present invention will be described in more detail by showing contrast between Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Organic solvents and compounds are described by the following abbreviations.

IPA: isopropyl alcohol

MEK: methyl ethyl ketone

DMF: N,N-dimethylformamide

DCM: dichloromethane

TFMB: 2,2'-bis(trifluoromethyl)benzidine

3,3'-DDS: 3,3'-diaminodiphenylsulfone

CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride

6FDA: 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

TMHQ: p-phenylenebis (trimellitic anhydride)

[Measurement of residual solvent amount]

The polyimide film|membrane residual solvent amount of an Example and a comparative example was measured with the following procedure.

Using about 8.9 g of 1,3-dioxolane as a solvent, about 0.1 g of a polyimide membrane and about 1 g of DEGBME (diethylene glycol butyl methyl ether) as an internal standard were dissolved to prepare a measurement sample. This sample was analyzed using a gas chromatograph (GC) apparatus (manufactured by Shimadzu Corporation), and the amount of residual solvent contained in the polyimide film was determined from the GC peak area and the preparation concentration.

[Production Example 1]

DMF was put into the reaction vessel and stirred under a nitrogen atmosphere. There, TFMB: 31 parts by weight, 3,3'-DDS: 10 parts by weight, CBDA: 18 parts by weight, and 6FDA: 21 parts by weight were sequentially added thereto, stirred for 10 hours in a nitrogen atmosphere, and a poly An amic acid solution was obtained. To 400 parts by weight of the polyamic acid solution, 36 parts by weight of pyridine as an imidization catalyst was added, and after complete dispersion, 46 parts by weight of acetic anhydride was added, stirred at 120° C. for 2 hours, and then cooled to room temperature. While stirring the solution, IPA was put in, and polyimide was deposited. Then, after performing suction filtration and repeating the washing|cleaning operation by IPA 4 times, it was made to dry in the vacuum oven set to 120 degreeC for 12 hours, and the polyimide resin 1 was obtained.

[Production Example 2]

DMF was put into the reaction vessel and stirred under a nitrogen atmosphere. There, TFMB: 17 parts by weight, 3,3'-DDS: 6 parts by weight, BPDA: 6 parts by weight, TMHQ: 9 parts by weight, and 6FDA: 17 parts by weight were sequentially added, and stirred for 5 hours under a nitrogen atmosphere, A polyamic acid solution having a solid content concentration of 18% was obtained. Then, it carried out similarly to manufacture example 1, imidation, precipitation of a polyimide, washing|cleaning and drying were performed, and the polyimide resin 2 was obtained.

[Comparative Example 1]

The polyimide resin 1 obtained by manufacture example 1 was melt|dissolved in MEK, and the polyimide resin solution of 13% of solid content concentration was obtained. Using a comma coater, a polyimide resin solution is applied on an alkali-free glass plate, dried at 40°C for 30 minutes and 70°C for 60 minutes in an atmospheric atmosphere, and then torn from the alkali-free glass plate, and a polyimide having a thickness of about 70 µm got a mid film. The residual MEK amount of this polyimide film was 9.4 weight%.

[Comparative Examples 2 and 3]

The polyimide film obtained in Comparative Example 1 was cut out to a size of about 12 cm 2 in area and immersed in water at room temperature (25° C.) for the time shown in Table 1, and then the water adhering to the surface was wiped off.

[Examples 1 to 6]

The solvent, temperature, and time of the immersion treatment were changed to the conditions shown in Table 1. Other than that, it carried out similarly to Comparative Examples 1 and 2, and performed the immersion process of a polyimide membrane. In Table 1, the ratio of the mixed solvent of Examples 1, 2, and 7 is a weight ratio. Details of the halogen-based mixed solvent used in Examples 3 to 6 are as follows.

Halogen-based mixed solvent 1: 50/50 (weight ratio) mixture of methylnonafluorobutyl ether/trans-1,2-dichloroethylene

Halogen-based mixed solvent 2: 53/44/3 (weight ratio) mixed solution of methylnonafluorobutyl ether/trans-1,2-dichloroethylene/ethanol

Halogen-based mixed solvent 3: 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane/trans-1,2- 15/85 (weight ratio) mixture of dichloroethylene/ethanol

[Comparative Example 4]

Polyimide resin 1 obtained in Production Example 1 was dissolved in a mixed solvent of MEK/DMF (volume ratio 70/30, weight ratio 67/37) to obtain a polyimide resin solution having a solid content concentration of 13%. Using a comma coater, a polyimide resin solution is applied on an alkali-free glass plate, dried at 40°C for 30 minutes and 70°C for 60 minutes in an atmospheric atmosphere, and then torn from the alkali-free glass plate, and a polyimide having a thickness of about 70 µm got a mid film. This polyimide film was cut out to the size of about 12 cm<2> in area, and it heated in 170 degreeC oven for 30 minutes.

[Example 7]

The polyimide film produced in the same manner as in Comparative Example 4 was cut into a size of about 12 cm 2 in area and immersed in a mixed solvent of methanol/water (volume ratio 60/40, weight ratio 54/46) heated to 60° C. for 30 minutes. , and heated in an oven at 170° C. for 30 minutes.

[Evaluation results of Examples 1 to 7 and Comparative Examples 1 to 4]

Table 1 shows the polyimide film treatment conditions (immersion treatment and heating conditions) of Examples 1 to 7 and Comparative Examples 1 to 4, and the amount of residual solvent after treatment.

In Comparative Examples 2 and 3, which were immersed in water, a sufficient reduction in the amount of residual solvent was not observed as compared with Comparative Example 1. In Examples 1 and 2, in which the immersion treatment was performed with a mixed solution of alcohol and water, the residual amount of MEK was significantly reduced compared to Comparative Examples 2 and 3, and in particular, in Example 2, in which the immersion treatment was performed under heating at 40 ° C. A significant decrease in the residual amount of MEK was observed. In Examples 3 to 6 using the halogen-based mixed solvent, the amount of residual MEK was lower than in Example 2 even in the treatment at room temperature. From these results, it is thought that the effect|action which removes (substitutes) the residual solvent in a polyimide film|membrane is high as for a halogen-type solvent.

In Comparative Example 4 in which heat treatment was performed at 170°C for 100 minutes without immersion treatment, residual MEK was not detected, but DMF, which is a high boiling point solvent, was not sufficiently removed. On the other hand, in Example 7 which heat-processed at 170 degreeC for 30 minutes after immersion in the mixed solvent of methanol and water for 30 minutes, the amount of residual DMF was also reduced significantly. The treatment time in Example 7 (60 minutes in total of 30 minutes of immersion and 30 minutes of heating) was shorter than the treatment time (100 minutes of heating) in Comparative Example 4, and the immersion treatment in the liquid for treatment was performed only by heating. It can be seen that the residual solvent can be removed more efficiently in a short time compared to the treatment.

[Example 8]

The polyimide film produced in the same manner as in Comparative Example 4 was cut to a size of about 12 cm 2 in area and hung inside a 500 mL separable flask filled with 200 mL of a mixed solvent of methanol/water (volume ratio 60/40, weight ratio 54/46). it was This separable flask was heated in a 60 degreeC oil bath for 30 minutes, and the polyimide film was exposed to the heated steam of alcohol and water. After heating at 170 degreeC for 60 minutes, when the residual solvent in a film was quantified by GC, DMF was 2.4 weight%, and MEK and methanol were not detected. It turns out that the residual solvent in a polyimide film|membrane can be reduced also by the exposure process to the heated steam of the liquid for a process similarly to an immersion process from this result.

[Comparative Example 5]

The polyimide resin 2 obtained by manufacture example 2 was melt|dissolved in DCM, and the polyimide resin solution of 18% of solid content concentration was obtained. Using a comma coater, a polyimide resin solution is applied on an alkali-free glass plate, dried at 40°C for 30 minutes and 70°C for 60 minutes in an atmospheric atmosphere, and then torn from the alkali-free glass plate, and a polyimide having a thickness of about 70 µm got a mid film. The amount of residual DCM of this polyimide film|membrane was 8.0 weight%.

[Comparative Example 6]

The polyimide film obtained in Comparative Example 5 was cut out to a size of about 12 cm 2 in area, and heated in an oven at 170°C for 60 minutes.

[Comparative Examples 7 and 8, Examples 9 to 14]

The polyimide film obtained in Comparative Example 5 was cut out to a size of about 12 cm 2 in area and treated to be immersed in a solvent under the conditions shown in Table 2, and then water adhering to the surface was wiped off. The halogen-based mixed solvent 1 used in Examples 10 and 11 is the same as that used in Examples 3 and 4. The glycol solvent used in Examples 12 to 14 was an 81/5/14 (weight ratio) mixture of diethylene glycol monobutyl ether/water/surfactant (polyoxyethylene alkyl ether, etc.).

[Evaluation results of Examples 9 to 14 and Comparative Examples 5 to 8]

Table 2 shows the polyimide film treatment conditions (immersion treatment and heating conditions) of Examples 9 to 14 and Comparative Examples 5 to 8, and the amount of DCM remaining after the treatment.

In Comparative Examples 7 and 8 in which the immersion treatment with water was performed, the amount of residual DCM was large compared to Comparative Example 6 in which the heat treatment was performed at 170°C for 60 minutes, and a sufficient reduction in the amount of the residual solvent was not observed. Comparative Examples in Example 9 in which an immersion treatment was performed with a mixed solution of alcohol and water, Examples 10 and 11 in which an immersion treatment was performed with a halogen-based mixed solvent, and Examples 12 to 14 which were subjected to an immersion treatment with a glycol ether-based solvent. It can be seen that the amount of residual DCM can be significantly reduced by the low-temperature and short-time treatment compared to the heat treatment of No. 6 .

[Example 15]

The polyimide film obtained in Comparative Example 5 was cut to a size of about 12 cm 2 in area, and halogen-based mixed solvent 1 was applied to the surface of the polyimide film using a bar coater, and the solvent adhering to the surface was wiped off after 20 minutes. . When the amount of DCM remaining in the film was quantified by GC, it was 0.1%. From this result, it turns out that the residual solvent in a polyimide film|membrane can be reduced also by the process which apply|coats the liquid for a process to the surface of a polyimide film similarly to an immersion process.

[Examples 16 and 17]

The film of Example 10 (which was immersed in the halogen-based mixed solvent 1 for 5 minutes) was heat-treated under the conditions shown in Table 3.

[Examples 18 and 19]

After immersing the film of Example 10 in water on the conditions shown in Table 3, it heated in 170 degreeC oven for 20 minutes.

[Examples 20 and 21]

The film of Example 10 was immersed in a mixed solvent of ethanol/IPA/water (weight ratio 45/5/50) under the conditions shown in Table 3, and then heated in an oven at 170°C for 20 minutes.

[Evaluation results of Examples 16 to 21]

Table 3 shows the polyimide film treatment conditions (immersion treatment and heating conditions) of Examples 16 to 21, and the amount of residual solvent after treatment. In addition, in Table 3, "immersion process 1" is a process on the same conditions as the immersion process in Example 10, and "immersion process 2" is a process performed after immersion process 1. HFE (hydrofluoroether) in Table 3 is methylnonafluorobutyl ether contained in the halogen-based mixed solvent 1.

From the result shown in Table 3, in the polyimide film of Example 10, the hydrofluoroether (HFE) contained in the halogen-type mixed solvent used for reduction of residual DCM remained in the polyimide film, and Example 16, 17 It can be seen that the amount of residual HFE is not sufficiently reduced even if the same heat treatment and immersion treatment with water as in Examples 18 and 19 are performed. On the other hand, it turns out that the residual amount of HFE can be reduced by performing a process using the mixed solvent of alcohol and water as a 2nd process liquid, and the residual amount of alcohol can also be reduced by heat-processing.

Claims (24)

A method for producing a transparent polyimide film, comprising:
a step of exposing a polyimide film containing an organic solvent to a liquid for a first treatment;
The first processing liquid,
without dissolving the polyimide film,
The content of water is 80% by weight or less,
A liquid having a flash point of 50 ° C. or higher, or a liquid not showing a flash point, or a mixture of alcohol and water having an alcohol content of 20% by weight or more and less than 60% by weight,
A method for producing a transparent polyimide film. The method of claim 1 , wherein the organic solvent has a flash point of 50° C. or higher, or does not exhibit a flash point. The method for producing a transparent polyimide film according to claim 2, wherein the boiling point of the organic solvent is 80°C or less. The method for producing a transparent polyimide film according to claim 1, wherein the organic solvent is dichloromethane. The polyimide film containing the organic solvent is produced according to any one of claims 1 to 4, wherein a solution in which the polyimide resin is dissolved in the organic solvent is applied on a support and a part of the organic solvent is removed. and,
The manufacturing method of the transparent polyimide film which exposes the said polyimide film containing the said organic solvent to the said 1st liquid for processing. The method for producing a transparent polyimide film according to claim 5, wherein the polyimide film is exposed to the first processing liquid after peeling the polyimide film from the support. The method for producing a transparent polyimide film according to any one of claims 1 to 6, wherein the transparent polyimide film is exposed to the liquid for the first treatment by directly contacting the liquid for the first treatment and the polyimide film. . The manufacturing method of the transparent polyimide film of Claim 7 in which the said polyimide film and the said liquid for a 1st process are made to contact by immersing the said polyimide film in the said liquid for a 1st process. The production of a transparent polyimide film according to any one of claims 1 to 6, wherein the polyimide film is exposed to the first processing liquid by exposing the polyimide film to a gas atmosphere of the first processing liquid. Way. The manufacturing method of the transparent polyimide film in any one of Claims 1-9 whose temperature at the time of exposing the said polyimide film to the said 1st liquid for a process is 30 degreeC or more. The manufacturing method of the transparent polyimide film in any one of Claims 1-10 in which the said 1st liquid for a process contains 20 weight% or more and less than 60 weight% alcohol, and 40 weight% or more of water. . The method for producing a transparent polyimide film according to claim 11, wherein the first processing liquid contains at least one alcohol selected from the group consisting of methanol, ethanol and isopropyl alcohol. The manufacturing method of the transparent polyimide film of Claim 11 or 12 in which the said 1st liquid for a process contains 2 or more types of alcohol. The manufacturing method of the transparent polyimide film in any one of Claims 1-10 in which the said 1st liquid for a process contains 20 weight% or more of organic fluorine-type solvents. The method for producing a transparent polyimide film according to claim 14, wherein the organic fluorine-based solvent is hydrofluoroether. The manufacturing method of the transparent polyimide film of Claim 14 or 15 in which the said 1st liquid for a process further contains the organic chlorine-type solvent which does not show solubility with respect to the said polyimide film. The glycol ether solvent according to any one of claims 1 to 10, wherein the first treatment liquid is selected from the group consisting of glycol ethers, dialkyl glycol ethers, and glycol ether acetates. A method for producing a transparent polyimide film comprising 20% by weight or more. The manufacturing method of the transparent polyimide film of Claim 17 in which the said 1st liquid for a process further contains water. The method for producing a transparent polyimide film according to any one of claims 1 to 18, wherein the first processing liquid is an azeotropic solvent containing two or more solvents. 20. The method according to any one of claims 1 to 19, further comprising, after the step of exposing the polyimide film to the first processing liquid, a step of exposing the polyimide film to the second processing liquid;
The second processing liquid,
has a composition different from that of the first processing liquid;
without dissolving the polyimide film,
The content of water is 80% by weight or less,
A liquid having a flash point of 50 ° C. or higher, or a liquid having no flash point, or a water mixture having an alcohol content of 20 wt% or more and less than 60 wt%,
A method for producing a transparent polyimide film. The liquid for a first treatment according to claim 20, wherein the first treatment liquid contains 20% by weight or more of an organic fluorine-based solvent, and the second treatment liquid contains 20% by weight or more and less than 60% by weight of alcohol and 40% by weight or more of water A method for producing a transparent polyimide film. The transparent polyimide according to any one of claims 1 to 21, wherein the transparent polyimide is 2,2-bis(3,4-dicarboxyphenyl)-1 in 100 mol% of a total of tetracarboxylic dianhydride components; A method for producing a transparent polyimide film, comprising 20 mol% or more of 1,1,3,3,3-hexafluoropropane dianhydride. The transparent polyimide according to any one of claims 1 to 22, wherein the transparent polyimide contains 20 mol% or more of 2,2'-bis(trifluoromethyl)benzidine in a total of 100 mol% of the diamine component. A method for producing a polyimide film. The manufacturing method of the transparent polyimide film in any one of Claims 1-23 whose film thickness of a transparent polyimide film is 5 micrometers or more.